This disclosure pertains to optical alignment in general, and in particular to a method and apparatus for multiple field-angle optical alignment testing.
Optical alignment involves adjustment of boresight, focus, or rotation, or any combination of two or more thereof. Boresight (in X and Y directions) can be set by measuring the position of a beam spot in the image. Focus (in Z direction) can be set by measuring the percentage of source energy (e.g., laser) that is captured when the spot is centered on a pixel of the image. Rotation (R) can be set by measuring a location of a beam spot at extreme positions in the image plane. These measurements are often accomplished at multiple beam angles. Conventionally, in order to vary the beam angle so as to perform the measurement at multiple beam angles, a lens being tested is often tilted repetitively relative to a collimated point source. The sequential tilting and mechanical motions of the lens can limit the accuracy and speed of the above measurements. In addition, the repetitive measurements at multiple angles increases the time needed to perform the alignment and thus increases the overall cost for alignment of the lens. The term “lens” is used herein to refer to any optical system including one, two or more optical lenses. In addition, the term “lens” is further used herein to refer to any optical system inclusive of reflective or refractive optical components.
One conventional method for performing optical alignment of the lens includes mounting the lens on a two-axis gimbal for viewing a collimated radiation source. A series of mechanical motions of the lens sets the different angular positions needed for measuring at multiple field angles. For example, in order to achieve boresight and rotation alignment of the lens, measurements are performed both prior and subsequent to alignment. Due to limited accuracy of mechanical motions, repetitive measurements are sometime required before achieving desired alignment accuracy. These repetitive measurements may prevent the alignment test/measurement from being rapid and may reduce the accuracy of the alignment. Indeed, the repetitive mechanical motions can make alignment a particularly time consuming and expensive operation.
Therefore, there is a need in the art for a system and method for multiple field angle optical alignment testing that provides an efficient and rapid as well as substantially accurate alignment.